Believe it or not, these co-stars weren’t filming an episode of ‘Gossip Girl’ when they stepped out all done up last night!

On practically every episode of Gossip Girl, there’s always a formal cocktail party or gala and the characters turn up all dressed up in gorgeous designer gowns. On Mar. 14, when Michelle Trachtenberg and Kelly Rutherford stepped out to attend the 2011 school of American Ballet winter ball it looked like they were filming an episode from the show — but in reality, they turned up to enjoy an evening at the ballet!

Michelle looked stunning in a plunging lilac Marchesa gown — the color was perfect against her hair and skin-tone. While Michelle went for a flowing look, Kelly opted for a more structured, one-shoulder Robin Brouillette gown. While I loved the dress, I think it would’ve looked best sans necklace.

Personally, I think Michelle looked better than ever with her hair swept back, keeping the focus on the flowing frock. Which dress did you like best last night?